Thank you for pointing that out and providing all that info. That is a known situation, actually.
The instance of Windows' speech engine that spins up when you launch VA does not poll to see if that device has been changed through Control Panel, nor does it respond to any event that Windows may have for that device changing/changed (this is the speech engine, outside of VA's control). Also, there is no active thread within VoiceAttack that polls the device settings, as that is a fairly, 'edge case' event (that is, the device that the speech engine is using is suddenly changed to something else is not something that happens a lot).
If you do need to change the recording device through Control Panel, you'll need to reset the Windows speech engine instance within VoiceAttack. If you have one of the later betas, you can click on the icon in the top-left corner of VA's main screen and select, 'Reset Speech Engine', or, you can include the, 'Reset Profile' action within a command.
If you don't have the latest beta, you can always open and close the options screen (can't remember if you have to make changes to the recognition-related stuff or not) or, close and restart VoiceAttack like the good old days. Either of those restart the Windows speech engine.
Hope that helps!